Heat exchanger and corresponding manufacturing method

ABSTRACT

A heat exchanger for an exhaust gas recirculation system includes an exchanger body delimiting an inner volume, and longitudinal tubes housed in the inner volume and forming a layer of tubes fitting between upper and lower planes. The tubes are separated by passages for circulating a second fluid, the upper plane being across from an upper part of the exchanger body. A second fluid inlet is arranged in the upper part of the exchanger body; and a member guides the second fluid in the inner volume. A deflector at least partially closes off the interstitial space between the upper part and the upper plane.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. non-provisional application claiming the benefit of French Application No. 18 56830, filed on Jul. 24, 2018, which is incorporated herein by its entirety.

FIELD OF INVENTION

The present invention relates in general to heat exchangers, in particular for motor vehicle exhaust lines.

BACKGROUND OF THE INVENTION

Such exchangers can include an exchanger body delimiting an inner volume and a plurality of longitudinal tubes housed in the inner volume, provided for the circulation of a first fluid, for example the exhaust gases. A second fluid, for example a coolant, circulates in the exchanger body, around tubes, from an inlet to an outlet.

A constant problem in this type of exchanger lies in preventing the second fluid from following the shortest path from the inlet to the outlet. If a large portion of the second fluid follows this short-circuit path, some areas of the tubes can be poorly cooled.

It is known to insert two combs around the tubes, oriented in opposite directions, to form a baffle forcing the second fluid to adopt an S-shaped journey from the inlet to the outlet.

Such an arrangement makes it possible to obtain a good quality heat exchange between the two fluids, but is mechanically complex.

In this context, the invention aims to propose a heat exchanger making it possible to obtain a good quality heat exchange between the two fluids, but which is mechanically less complex.

SUMMARY OF THE INVENTION

A heat exchanger for an exhaust gas recirculation system includes an exchanger body delimiting an inner volume; a plurality of longitudinal tubes housed in the inner volume, provided to circulate a first fluid, at least some of the tubes being transversely juxtaposed and forming a layer of tubes fitting between upper and lower planes, the tubes of said layer of tubes being separated from one another by passages for circulating a second fluid, at least the upper plane containing the longitudinal and transverse directions, the upper plane being directly across from an upper part of the exchanger body and being separated from the latter by an interstitial space; a second fluid inlet emerging in the inner volume, arranged in the upper part of the exchanger body; and a guide member for guiding the second fluid in the inner body, including a deflector having a transverse zone at least partially closing off the interstitial space between the upper part and the upper plane.

The deflector prevents the second fluid from adopting an essentially longitudinal flow at the mouth of the second fluid inlet. It deflects the second fluid depthwise in the passages, which contributes to obtaining a satisfactory thermal exchange quality between the fluids.

The heat exchanger may also have one or more of the features below, considered individually or according to any technical possible combination(s):

the guide member comprises a grid for distributing the second fluid, arranged in the interstitial space between the upper part and the upper plane, across from the second fluid inlet;

the deflector of the guide member comprises teeth engaged in the passages;

the distribution grid, the transverse zone and the teeth are integral with one another;

the distribution grid, the transverse zone and the teeth are formed in a same metal plate;

the distribution grid extends over substantially the entire width of the layer of tubes and has, across from each passage, at least one hole, the second fluid inlet being placed across from at least one central passage from among the passages, the at least one hole having a passage section increasing transversely from the at least one central passage;

each tooth extends transversely over the entire width of the corresponding passage;

each passage extends over a determined height along an elevation direction substantially perpendicular to the longitudinal and transverse directions, the corresponding tooth extending over a height comprised between 5% and 50% of said determined height;

at least one of the two tubes surrounding said passage has a rib protruding in the passage, extending the tooth in the elevation direction, the rib preferably having interruptions;

According to a second aspect, the invention relates to a method for manufacturing a heat exchanger having the features above, comprising the following steps: forming the guide member for guiding the second fluid, by cutting and shaping a metal plate; placing the longitudinal tubes and the guide member in the exchanger body; and fastening the longitudinal tubes, the guide member and the exchanger body to one another.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention will emerge from the detailed description given below, by way of indication and without limitation, with reference to the annexed figures, including:

FIG. 1 is a simplified schematic illustration of a heat exchanger according to the invention;

FIG. 2 is a partial perspective view of the heat exchanger of FIG. 1, the body being shown translucent so that the tubes and the guide member for guiding the second fluid are visible;

FIG. 3 is a sectional view of the heat exchanger of FIG. 2 in a plane perpendicular to the longitudinal direction, considered along the incidence of arrows III;

FIG. 4 is a partial perspective view of the heat exchanger of FIG. 2, the body being shown translucent so that the tubes and the guide member for guiding the second fluid are visible;

FIG. 5 is a perspective view of the guide member for guiding the second fluid of FIG. 2;

FIG. 6 illustrates the plate from which the guide member for guiding the second fluid is manufactured;

FIG. 7 illustrates the state of the plate of FIG. 6 after the cutting operation and before the shaping operation; and

FIG. 8 is an elevation view of a zone of a tube delimiting one of the second fluid passages, showing the rib extending the tooth engaged in said passage.

DETAILED DESCRIPTION

The heat exchanger 1 shown in FIG. 1 is intended to be inserted into a vehicle exhaust line, in particular of a motor vehicle such as a car or truck.

This heat exchanger is, for example, inserted on the EGR (Exhaust Gas Recycling) line, which makes it possible to recycle part of the exhaust gases toward the inlet of the combustion chamber of the engine, mixed with fresh air.

In a variant, the heat exchanger is integrated into an EHRS (Exhaust Heat Recovery System) device or into any other system of the exhaust line.

According to another variant, the heat exchanger is integrated into another circuit of the vehicle, or even into a static system, which is not on board a vehicle.

The heat exchanger 1 is provided to place a first fluid and a second fluid in thermal contact.

The first fluid is, for example, the exhaust gases of the vehicle, the second fluid being a heat transfer fluid intended to cool the exhaust gases. The second fluid is, for example, a liquid such as water with potential additives.

In a variant, both fluids are of any other type.

The heat exchanger 1 includes an exchanger body 3 delimiting an inner volume 5 and a plurality of longitudinal tubes 7 housed in the inner volume 5 (FIGS. 2 and 3).

The tubes 7 are provided to circulate the first fluid.

The exchanger body 3 includes a tubular wall 9, with a longitudinal central axis. In the illustrated example, the tubular wall 9 is a cylinder with a substantially rectangular straight section.

The tubes 7 are typically all identical. They are rectilinear, with a substantially rectangular section. They are parallel to one another.

Each tube 7, considered in section in a plane perpendicular to the longitudinal direction, is thus delimited by two opposite side faces 11 that are opposite one another, an upper face 13 and a lower face 15. The upper and lower faces 13, 15 connect the side faces 11 to one another.

The side faces 11 are substantially planar and perpendicular to a transverse direction. The transverse direction is perpendicular to the longitudinal direction.

At least a portion of the tubes 7 is transversely adjacent and forms a layer of tubes fitting between upper and lower planes P1 and P2 (FIG. 3). The tubes 7 of said layer are separated from one another by circulation passages 19 for the second fluid.

In the illustrated example, all of the tubes 7 are juxtaposed in a single layer.

The tubes 7 are arranged such that their side faces 11 are placed opposite one another. Each passage 19 is thus delimited by the faces 11 of two adjacent tubes in the layer.

The layer typically includes a large number of tubes, for example at least 5.

Each tube 7 has a large height, considered in an elevation direction, compared with its width considered in the transverse direction. The elevation direction E is substantially perpendicular to the longitudinal and transverse directions L and T. These directions are shown by arrows in FIGS. 2 and 3.

The tubes 7 extend over substantially the entire longitudinal length of the tubular wall 9.

The exchanger body 3 includes two end plates 21, engaged in the two opposite longitudinal ends of the tubular wall 9 (FIGS. 2 to 4). The tubular wall 9 has, at each of its longitudinal ends, an edge with a closed contour 23, fastened sealably to the corresponding end plate 21.

Each end plate 21 has a plurality of oblong orifices 25, transversely juxtaposed. Each tube 7 has a longitudinal end fastened sealably to the peripheral edge of one of the oblong orifices of the first of the two plates, its opposite longitudinal end being sealably fastened to the peripheral edge of one of the oblong orifices of the other of the two plates (FIG. 4).

Thus, the inner volume 5 provided for the circulation of the second fluid is delimited by the tubular wall 9 and the end plates 21.

The upper plane P1 typically corresponds to a plane containing the longitudinal and transverse directions, tangent to at least one of the tubes 7 without intersecting the other tubes. It is shown in FIG. 3. It is tangent to the upper face 13 of at least one tube 7. In the illustrated example, the upper faces 13 of the tubes 7 fit in the upper plane P1.

The lower plane P2 is also typically a plane containing the longitudinal and transverse directions, tangent to at least one of the tubes 7 without intersecting the other tubes. It is shown in FIG. 3. It is tangent to the lower face 15 of at least one tube 7. In the illustrated example, the lower faces 15 of the tubes 7 fit in the lower plane P2.

The upper plane P1 is directly across from an upper part 27 of the exchanger body 3 and is separated therefrom by an interstitial space 29.

The interstitial space 29 typically extends over the entire transverse width of the layer of tubes and over the entire longitudinal length of the layer of tubes. It constitutes a favored leak path for the second fluid.

A second fluid inlet 31 opening out into the inner volume 5 is arranged in the upper part 27 of the exchanger body 3 (FIG. 1).

A second fluid outlet 33 opening out into the inner volume 5 is also arranged in the exchanger body 3.

As shown in FIG. 1, the second fluid inlet 31 is arranged on a first longitudinal half of the exchanger body 3, the second fluid outlet 33 being arranged on a second longitudinal half of the exchanger body 3 opposite the first half.

The heat exchanger 1 further includes a guide member 35 for guiding the second fluid in the inner volume 5, including:

a grid 37 for distributing the second fluid, arranged in the interstitial space 29 between the upper part 27 and the upper plane P1, across from the second fluid inlet 31;

a deflector 39 having a transverse zone 41 at least partially closing off the interstitial space 29 between the upper part 27 and the upper plane P1, and teeth 43 engaged in the passages 19.

This guide member is in particular shown in FIG. 5.

It is provided to guide the second fluid circulating in the inner volume 5, from the second fluid inlet 31 to the second fluid outlet 33, so as to improve the distribution of second fluid in the passages 19.

The distribution grid 37, the transverse zone 41 and the teeth 43 are integral with one another.

More specifically, the distribution grid 37, the transverse zone 41 and the teeth 43 are formed in a same metal plate 49, as shown in FIGS. 5 to 7.

The distribution grid 37 is a planar zone of the metal plate 49, typically extending in a longitudinal and transverse plane, for example the upper plane P1. It extends over the entire width of the layer of tubes. It is typically placed on the upper faces 13 of the tubes 7 and rigidly fastened to the tubes 7.

The distribution grid 37 has, opposite each passage 19, at least one hole 51 (FIG. 4). Typically, it has a single hole 51 opposite each passage 19. The holes 51 are therefore transversely aligned.

The second fluid inlet 31 is placed opposite at least one central passage, here referenced 53, among the passages 19.

In the illustrated example, two so-called central passages 53 are located across from the inlet 31, as shown in FIG. 3.

The inlet 31, in the transverse direction, is substantially at the center of the layer of tubes.

The at least one hole 51 has a passage section increasing transversely from the at least one central passage 53.

The considered passage section is the total section, offered collectively to the second fluid by the hole(s) 51 associated with the second fluid passage 19.

This means that the passage section offered to the second fluid is relatively smaller for the hole(s) 51 associated with the central passages 53. The passage section offered to the second fluid is slightly bigger for the hole(s) 51 associated with the two second fluid passages 19 adjoining the central passages 53. The passage section of the holes increases gradually as one moves transversely away from the central passages.

Such an arrangement makes it possible to distribute the second fluid arriving through the inlet 31 uniformly in the passages 19.

The transverse zone 41 is defined by a solid part of the plate 49. It includes two flaps 55, 57, of the same shape, pressed on one another. The two flaps 55, 57 are exactly superimposed on one another, as shown in FIG. 5.

The flaps 55 and 57 are connected to one another by an upper bending line 59 of the plate 49, oriented transversely. The flap 55 is connected to a transverse edge of the grid 37 by a lower bending line 61, oriented transversely (FIG. 7).

The teeth 43 are secured to a transverse edge 63 of the flap 57, opposite the upper bending line 59.

The flaps 55 and 57 extend in a plane containing the elevation direction and the transverse direction. They are substantially perpendicular to the distribution grid 37.

The transverse zone 41 closes off at least 90% of the cross-section of the interstitial space 29, preferably at least 95% of said cross-section, still more preferably at least 98% of said cross-section.

As illustrated in FIG. 3, the cross-section 41 fits in a determined transverse plane. The interstitial space 29 has a determined inner section in said transverse plane. The outer section of the transverse zone 41 is substantially conjugated with the inner section of the interstitial space 29 in said plane.

The second fluid inlet 31 is arranged on a boss 65 formed in the exchanger body 3 (FIGS. 2 and 3).

This boss 65 is convex toward the outside of the exchanger body 3. The inlet 31 is formed at the apex of the boss 65.

The transverse zone 41 typically fits in a transverse plane intersecting the boss 65. It therefore has a truncated pyramid shape, as illustrated in FIG. 3.

The upper bending line 59 constitutes the upper edge of the transverse zone 41 and points toward the upper zone 27 of the exchanger body 3. It is shorter in the transverse direction than the lower bending line 61 and the transverse edge 63.

The upper bending line 59 is connected to the lower bending line 61 by oblique edges 67 of the flap 55. It is connected to the transverse edge 63 by oblique edges 69 of the flap 57, which are superimposed exactly on the oblique edges 67.

The transverse zone 41 is inserted longitudinally between the second fluid inlet 31 and the second fluid outlet 33.

The teeth 43 are all attached to the transverse zone 41.

They come from the transverse edge 63 of the flap 57. They are regularly spaced apart along the transverse edge 63.

Each second fluid circulation passage 19 receives one of the teeth 43.

According to one embodiment variant that is not shown, one of the teeth 43 is inserted between the exchanger body 3 and the tube 7 located at the first transverse end of the layer. Another one of the teeth 43 is inserted between the exchanger body 3 and the tube 7 located at the second transverse end of the layer.

Each tooth 43 extends transversely over the entire width of the corresponding passage 19.

The teeth 43 are for example L-shaped, with a free segment 71 oriented along the elevation direction, and an intermediate segment oriented substantially longitudinally connecting the free segment 73 to the transverse zone 41.

Each passage 19 extends over a determined height in the elevation direction. The corresponding tooth 43 extending over a height of between 5% and 50% of said determined height, preferably between 10% and 30% of said determined height, still more preferably between 10% and 20% of said determined height.

Preferably, at least one of the two tubes 7 surrounding said passage 19 has a rib 75 protruding in the passage 19, extending the tooth 43 in the elevation direction. The rib 75 is in particular visible in FIG. 8. It is formed on the side face 11 of the tube.

Typically, the two tubes 7 surrounding said passage 19 each have a rib 75 protruding in the passage 19. These ribs are substantially identical.

Each rib 75 typically extends at least from the upper face 13 over at least 50% of the height of the tube 7 considered along the elevation direction E.

In the example illustrated in FIG. 4, the rib 75 extends first, from the upper face 13, along the elevation direction, then along an inclined direction oriented longitudinally toward the end plate 21 and along the elevation direction toward the lower face 15.

The two ribs 75 are placed opposite one another along the transverse direction. Together, they close off the passage 19 over substantially its entire transverse width. To that end, each rib 75 protrudes relative to the side face 11 of the corresponding tube 7 over a height such that it practically touches the rib 75 opposite it.

The rib 75 preferably has interruptions 77, typically regularly spaced apart. This makes it possible to create a flow of second fluid in the passage immediately behind the rib 75, which makes it possible to obtain a more uniform temperature field along the tube.

FIG. 8 shows that each tube 7 includes reliefs 79 in pad form, formed by deformation of the side wall 11 of the tube. These reliefs are spacers making it possible to guarantee the separation between the tubes 7, and therefore the width of the passage 19.

The operation of the heat exchanger will now be described.

The first fluid penetrates the heat exchanger by a longitudinal end of the tubes 7. It circulates along the tubes 7 and leaves the heat exchanger at the other longitudinal end of the tubes 7.

The second fluid penetrates the heat exchanger through the second fluid inlet 31. It flows in the inner volume 5.

The second fluid, upon leaving the inlet 31, is found in the interstitial space 29. It cannot flow longitudinally along the interstitial space 29 toward the outlet 33, due to the presence of the transverse zone.

It is therefore forced to pass through the distribution grid 37 and penetrate inside the circulation passages 19.

The hole(s) 51 covering the central passage(s) 53, located opposite the inlet 31, are relatively smaller and offer a relatively greater resistance to the flow of the fluid. On the contrary, the hole(s) 51 covering the passage(s) 19 transversely offset relative to the inlet 31 are relatively larger and offer a relatively weaker resistance to the flow of the fluid.

As a result, the second fluid is distributed substantially uniformly in the different passages 19, the different passages 19 receiving respective fluid flow rates close to one another.

The teeth 43 prevent the second fluid from circulating, in a same passage 19, essentially longitudinally in the zone located immediately below the interstitial space 9.

The teeth 43 deflect the second fluid toward the lower face of the tube, depthwise in the passage 19.

The ribs 75 extend this movement, and deflect the second fluid even more depthwise in the passages 19, in a direction opposite the interstitial space 9. A low flow rate of second fluid passes through the interruptions 77.

When the second fluid reaches the end of the ribs 75, it flows longitudinally toward the second fluid outlet 33.

The invention also relates to a method for manufacturing a heat exchanger 1 having the above features.

The manufacturing method comprises the following steps:

Forming the guide member 39 of the second fluid, by cutting and shaping a metal plate;

Placing the longitudinal tubes 7 and the guide member 39 in the exchanger body 3;

Fastening the longitudinal tubes 7, the guide member 39 and the exchanger body 3 together.

The metal plate 49 from which the guide member is manufactured is illustrated in FIG. 6.

It is typically flat, and has a thickness of between 0.2 and 1 mm, advantageously between 0.3 and 0.8 mm, and still more advantageously 0.4 mm. It is made from steel, preferably austenitic steel.

The cutting and shaping step comprises an operation for cutting the plate 49, so as to delimit the contour of the distribution grid and create the holes 51.

The cutting also makes it possible to create the oblique edges 67, 69, and the teeth 43.

The state of the plate 49 after the cutting operation is illustrated in FIG. 7.

The cutting and shaping step comprises a shaping operation, during which the plate 49 is bent substantially at 90° around the lower bending line 61, and 180° around the upper bending line 59.

The shaping operation also makes it possible to shape the teeth 43.

The shaping operation is done after or at the same time as the cutting operation.

The bending and shaping step is, for example, a stamping step.

The fastening of the longitudinal tubes 7, the guide member 39 and the exchanger body 3 to one another is typically done by brazing, in a furnace.

In the present description, reference has been made to upper and lower faces or directions. The upper face and the upper direction are not necessarily oriented toward the top and can be oriented in any direction. The same comment applies to the lower face and the lower direction.

The heat exchanger can have multiple variants.

According to one variant, the tubes are arranged in several layers, superimposed on one another in the elevation direction.

The two ribs protruding in the second fluid circulation passage, arranged opposite one another, can be replaced by a single rib, carried by one of the two tubes.

The exchanger body and the tubes have any appropriate shapes.

The inlet is not necessarily formed on a boss. In a variant, it is formed in a zone that does not protrude on the exchanger body.

The invention has multiple advantages.

The guide member is particularly easy and inexpensive to manufacture because the distribution grid, the transverse zone and the teeth are formed in a same metal plate.

The fact that the transverse zone closes off at least 90% of a cross-section of the interstitial space contributes to obtaining a good distribution of the second fluid in the inner volume of the exchanger body, due to the absence of short-circuit path from the inlet to the outlet.

The fact that the transverse zone is inserted longitudinally between the second fluid inlet and the second fluid outlet also contributes to the good distribution of the second fluid.

When the second fluid inlet is arranged on a boss formed in the exchanger body, the distribution of the second fluid from the inlet is made easier. The transverse zone blocks the circulation of the fluid longitudinally in the interstitial space as close as possible to the inlet.

The teeth block the circulation of the second fluid longitudinally in the upper part of the passages, immediately below the interstitial space. It is not possible to form ribs on the tubes in this location, since these ribs would be too close to the junction edge between the side face and the upper face of the tubes.

Using protruding ribs formed in the tubes in the extension of the teeth makes it possible to deflect the second fluid conveniently. These ribs are inexpensive to produce and easy to implement.

Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. For that reason, the following claims should be studied to determine the true scope and content of this disclosure. 

1. A heat exchanger for an exhaust gas recirculation system, comprising: an exchanger body delimiting an inner volume; a plurality of longitudinal tubes housed in the inner volume and provided to circulate a first fluid, at least some of the longitudinal tubes being transversely juxtaposed and forming a layer of longitudinal tubes fitting between upper and lower planes, the longitudinal tubes of said layer of longitudinal tubes being separated from one another by passages for circulating a second fluid, at least the upper plane including longitudinal and transverse directions, the upper plane being directly across from an upper part of the exchanger body and being separated from the exchanger body by an interstitial space; a second fluid inlet opening out into the inner volume and arranged in the upper part of the exchanger body; and a guide member to guide the second fluid in the inner volume, and including a deflector having a transverse zone at least partially closing off the interstitial space between the upper part and the upper plane.
 2. The heat exchanger according to claim 1, wherein the guide member comprises a grid that distributes the second fluid, the grid being arranged in the interstitial space between the upper part and the upper plane, across from the second fluid inlet.
 3. The heat exchanger according to claim 2, wherein the distribution grid extends over substantially an entire width of the layer of longitudinal tubes and has, across from each passage, at least one hole, the second fluid inlet being placed across from at least one central passage from among the passages, the at least one hole having a passage section increasing transversely from the at least one central passage.
 4. The heat exchanger according to claim 2, wherein the deflector of the guide member comprises teeth engaged in the passages.
 5. The heat exchanger according to claim 4, wherein the distribution grid, the transverse zone, and the teeth are integral with one another.
 6. The heat exchanger according to claim 4, wherein the distribution grid, the transverse zone, and the teeth are formed in a same metal plate.
 7. The heat exchanger according to claim 4, wherein each tooth extends transversely over an entire width of the corresponding passage.
 8. The heat exchanger according to claim 4, wherein each passage extends over a determined height along an elevation direction substantially perpendicular to the longitudinal and transverse directions, the corresponding tooth extending over a height comprised between 5% and 50% of said determined height.
 9. The heat exchanger according to claim 8, wherein at least one of two longitudinal tubes surrounding said passage has a rib protruding in the passage, extending the tooth in the elevation direction, the rib preferably having interruptions.
 10. A method for manufacturing a heat exchanger according to claim 1, the manufacturing method comprising the following steps: Forming the guide member that guides the second fluid, by cutting and shaping a metal plate; Placing the longitudinal tubes and the guide member in the exchanger body; and Fastening the longitudinal tubes, the guide member, and the exchanger body together. 